History helps us find out how things might happen,' says Tim Jackaman as an October rain-shower forces PRWeek from his office veranda and into the dry.

‘It's the same in PR - if you've experienced a certain situation then you can predict how a similar one might turn out.' Jackaman may not have been able to forecast the weather, but his 25 years in City PR enable him to sound convincing when expounding on the industry's future and his role in it.

The 48-year-old is chairman of GreenTarget, which he launched in London this year after a two-year break. The Square Mile co-founder called the start-up GJR, after his and colleagues Melissa Rowling and Nick Glanvil's initials, but the agency last month merged with former Shandwick US financial practice chief Daniel Reid's Chicago-based consultancy Green­Target (PRWeek, 22 Sep).

Jackaman is quietly authoritative with a dress-sense that errs towards the loud. His evidently jolly relationship with staff at GreenTarget's White­chapel office on the edge of the City is perhaps an indicator of why he has achieved industry longevity.

Former Manning Selvage & Lee MD Jackie Elliot, who was once in talks with Jackaman about MS&L investing in Square Mile, describes him as ‘always congenial, carefully insightful and an all-round lovely bloke'.

Jackaman arrived in PR in the 1980s after a stint in journalism - he admits he did not have a tabloid hack's nose for news. ‘I couldn't spot something innocuous and turn it into something fabulous,' he concedes. ‘I moved into the City because it was an area I felt I could get my teeth into.'

The fact Jackaman knew little about the ins-and-outs of London's financial centre, he says, appealed to him. A similar perverse curiosity, he says, explains his decision to take his two-year industry break to study for a Masters in History at the University of Kent.

‘There was a gap in my understanding,' he says. ‘History has relevance in communication because bias affects historical texts in the same way that it acts upon the opinions of the public and the messages companies give out.'

His early PR career included a spell at Hill & Knowlton in Hong Kong. ‘1985 and 1986 were great years because so much was happening out there,' he recalls excitedly. ‘A unit trust would grow ten per cent in a week.'

But Jackaman's biggest success, and the role that made his name in City PR circles, was co-founding and developing Square Mile.

‘I joined just after [Square Mile] started up,' he recounts. ‘[Co-founder] Susan Ellis was a great manager - we steered the agency through one of the industry's biggest downturns.'

Ellis worked alongside Jackaman for 15 years. She says: ‘He is an ideas-man. I was an "implementor" - it worked well because he wasn't the most organised!'

During the early-1990s recession, PR was a hard sell; boards saw it as a last resort and questioned its value, says Jackaman.

‘Now the buying of PR is sophisticated and what matters to companies has changed a great deal,' he says. ‘Life is not just about profit. Good relationships with government, and environmental concerns will have a huge bearing on performance.' Nonetheless he believes big agencies are yet to make their clout count. ‘I've yet to see a big player make the most of its size,' Jackaman argues. ‘It's much harder for a big agency to seem hungry.'

Jackaman's views are unsurprising. Having left a big agency - Weber Shandwick - after the end of his earnout (WS Square Mile was formed in 2001 after Interpublic Group's Weber Shandwick Worldwide and BSMG Worldwide merged), he has no plans to go toe-to-toe with bigger rivals.

‘The Financial Dynamics and Brunswicks have the M&A market sewn up,' he says. ‘I'm not interested in that. I want something to get my teeth into - financial services and ethical issues, sectors with interesting audiences. It really is difficult to get excited about reporting results. I want to help businesses explain themselves.'